This invention relates to a bus bar for electrical power distribution.
In the field of electrical power devices, a wide range of devices are known and currently available for distributing, converting, producing, and applying power. Depending upon the application, such devices may distribute incoming power to various devices and/or convert incoming power from one form to another as needed by a load. In a typical drive system arrangement, for example, constant (or varying) frequency alternating current power (such as from a utility grid or generator) is converted to controlled frequency alternating current power to drive motors, and other loads. In this type of application, the frequency of the output power can be regulated to control the speed of the motor or other device. Further, drive system buses may distribute the power throughout the process. In a motor control center application, a bus system may facilitate distribution of power to a number of system components and devices. For example, a motor control center bus may be utilized to provide power to a drive system bus. Further, such electrical installations may include bus work that communicatively couples the components with a power source and/or other components.
Bus bars 1 for electrical distribution have been in the form of metallic straps which are first cut to length and then provided with sets of holes 3 through which bolts 5 are received for mounting the bus bars on suitable supports within a cabinet, for connecting them to each other, and for mounting electrical cable connectors 7 for conductors 9 thereon as shown generally in FIGS. 1A and 1B. Usually the locations of the holes 3 are predetermined for specific arrangements, the holes being punched by the manufacturer at precise predetermined positions.
Moreover, with the prior art bus bars and the associated supports, a technician needs to have access underneath the bus bar for a wrench or the like for securing the supports and bus bar to each other and the supporting surface. As a result, the height of the bus bar from the supporting surface is significant to provide for clearance and required access.
The use of holes in specific positions along the bus bars limits the possible positions of the bus bars relative to each other and to supporting structure to specific arrangements of the original design. Consequently, for each different type and size of installation, holes have to be specially laid out and punched in the bus bars. Considerable layout time and expense is involved in positioning and punching the selected holes. This is both inefficient and labor intensive.
Another undesirable feature of prior bus bar designs is that the current carrying capacity of the bars is not uniform for all cross sections throughout its length as the total cross section for conducting metal is reduced at those areas in which the holes are provided relative to those areas in which no hole is provided. Accordingly, assuming a bar of uniform thickness and overall width, to provide an amount of conducting cross section at the location of the holes sufficient to meet the rated maximum current carrying capacity of the bar results in an excess of conducting cross section at the imperforate portions, and a resultant waste or inefficient use of the metal.
Traditionally, such bus work is manufactured to a specific length with punched holes or a combination of cabling and bus work to provide for electrical transmission to components. Such bus work may be directly affixed to an electrical enclosure by a fastener (e.g., a nut and bolt assembly) and a non-conductive standoff. Such bus work and attachment features can be complex, expensive, nonadjustable and/or difficult to configure. Many such bus bars must comply with standards for the hole spacing such as NEMA 1.7. Traditional bus work may be generally cumbersome and only enable coupling of attachment features at specific locations on the bus (e.g., punched holes along the bus). Additionally, traditional bus systems and support structures require substantial changes to accommodate different amperage levels or installation requirements.
Accordingly, it is now recognized that it would be desirable to develop a bus system that facilitates electrical conductivity and the like in a flexible configuration, enables simplified manufacturing changes to accommodate different amperage levels and electrical enclosure arrangements, enables convenient coupling of attachment features at generally any location along the bus and delivers consistent capacity along the bus bar.